This application claims priority of Korea patent Application No. 10-2000-0063893, filed on Oct. 30, 2000.
(a) Field of the Invention
The present invention relates to a gear shift control method for automotive vehicles. More specifically, the present invention relates to a kick-down control method for improving shift response in controlling fifth-to-third or fifth-to-second gear skip-shifting.
(b) Description of the Related Art
In general, an automotive vehicle equipped with an automatic transmission controls hydraulic pressure in a preset fashion based on the running speed of the vehicle, to automatically change gears to a target gear.
The automotive vehicle actuates a torque converter according to the output power of an engine to transfer the power to the transmission, and to make the hydraulic pressure operative to a particular valve based on a control signal applied from a transmission control unit so that a corresponding gear change operation occurs according to the operational status of the vehicle.
In such an automotive vehicle with an automatic transmission of which the operational status is controlled based on hydraulic pressure, the driver does not have to manipulate a clutch pedal to interrupt power from the engine while changing gears, so that he/she has less driving fatigue and rarely encounters an engine stall caused by malfunction or inexperience. It is thus easy for a beginner to drive such an automotive vehicle with an automatic transmission.
The output power of a planetary gear set is changed based on the selective operation of friction members that comprise, for example, clutches and brakes, to output adequate shift ratios, and the power is transmitted to a drive gear. The changed power is then transmitted to a slave gear, which is meshed with a final speed-up gear, by means of a driven gear meshed with the drive gear to control the rotation of wheels.
Regulating the status of the hydraulic pressure generated by way of the torque converter to control shifting to a target gear, especially fifth-to-third or fifth-to-second gear kick-down shifting, can be performed in conventional hydraulic control systems as illustrated in FIG. 1. It includes: a fifth-to-fourth gear shifting stage during which a release control on a release side of a secondary shift part that operates in fifth speed is performed according to a duty pattern xe2x80x9caxe2x80x9d of FIG. 1, and a coupling control on a coupling side of the second shift part that operates in fourth speed is then performed according to a duty pattern xe2x80x9ccxe2x80x9d of FIG. 1 and a fourth-to-third or fourth-to-second gear shifting stage during which a release control on a release side of a primary shift part is performed according to a duty pattern xe2x80x9cbxe2x80x9d of FIG. 1, and a coupling control on a coupling side of the primary shift part is then performed according to a duty pattern xe2x80x9cdxe2x80x9d of FIG. 1.
Due to a hold time that corresponds to a time interval xe2x80x9cExe2x80x9d for control on the coupling side as performed by the secondary shift part control and a time interval of adverse slope control on the release side by the primary shift control, shift response is slow and maintenance of the engine rpm occurs during the hold time so that the driver is easily irritated by the slow gear shifting with respect to a feeling of acceleration.
It is an object of the present invention to solve the problems with the prior art and to reduce a hold time during fifth-to-third or fifth-to-second gear kick-down shifting to improve shift feel.
In one aspect of the present invention, there is provided a method for improving kick-down shift response of a five-speed automatic transmission by reducing a hold time during fifth-to-third or fifth-to-second gear shifting by using: a turbine rpm sensor of which the operational status is varied based on the rotational status of a turbine connected to an input shaft of the automatic transmission, to determine the rpm of the turbine; a transmission output shaft rpm sensor that detects a transmission output shaft rpm; a transmission control unit that controls a gear shift of the transmission by outputting shift signals; and a hydraulic pressure control system that performs the gear shifting by-being inputted the gear shift signal.
The method for improving kick-down shift response of a five-speed automatic transmission in accordance with the present invention includes:
(a) detecting a fifth-to-third or fifth-to-second gear shifting signal;
(b) performing fifth-to-fourth gear shifting by performing a duty control on a secondary shift part if the fifth-to-third or fifth-to-second gear shifting signal is detected in step (a);
(c) determining a starting point of duty control on a release side of a primary shift part, and performing duty control on the release side of the primary shift part; and
(d) performing duty control on a coupling part of the primary shift part.